Salinity pollution from irrigated agriculture

Excerpt

SALINITY pollution is not a recent phenomenon resulting from industrialization or the modernization of agriculture, but an age-old problem of irrigated agriculture thought to have caused the decline of certain ancient civilizations. Six thousand years ago, on the Tigris-Euphrates floodplain in Mesopotamia, Sumerian irrigation practices caused a salt build-up in water and soils that inhibited food production and no doubt contributed to the decline of Sumerian culture. In the American Southwest, the decline of Indian civilizations, centuries ago, is also attributed to salinization of land and water.

Soil and water salinity occur in arid and semiarid regions wherever irrigated agriculture is practiced. Today, salinity seriously affects productivity on about 50 million acres (20 million hectares) of the worlds irrigated land (14). In the United States, an estimated 20 to 25 percent of all irrigated land [about 10 million acres (4 million hectares)] suffers from salt-caused yield reductions (2). Though less menacing than pollution from heavy metals or toxic organic compounds, salinity constitutes the most serious water quality problem in many arid and semiarid river basins.

In the United States, irrigated agriculture in 1977 accounted for 82 percent of all water consumption, 47 percent of all diversions …